Wafer-capped rechargeable power source

ABSTRACT

Embodiments of the present invention may provide a wafer-capped rechargeable power source. The wafer-capped rechargeable power source may comprise a device wafer, a rechargeable power source disposed on a surface of the device wafer, and a capping wafer to encapsulate the rechargeable power source. The rechargeable power source may include an anode component, a cathode component, and an electrolyte component.

BACKGROUND

The present invention relates to rechargeable power sources.

Electronic devices, such as smartphones, laptops, digital cameras,watches, etc., generally require a power source, which is usuallyprovided in the form of rechargeable battery packs. These rechargeablebattery packs typically account for a major portion of the size andweight of the electronic devices. With an ongoing need to miniaturizeand/or lighten such electronic devices, it is desirable to find newsolutions for powering these electronic devices.

Given that most electronic devices include a plurality of integratedcircuits, one solution is to fabricate the rechargeable power sourcesalso on integrated circuits. While there are existing techniques tofabricate rechargeable batteries on substrates, the materials being usedfor the batteries are typically flammable and/or sensitive to hightemperatures, which are common in the manufacturing of integratedcircuits. These materials being also usually sensitive to moisture, itis desirable to have them hermetically sealed.

Therefore, the inventor perceives a need in the art for a rechargeablepower source that may maintain its power capacity over time and that maybe fabricated on a substrate and included in an integrated circuit,while reducing the risk of explosion of the rechargeable power sourceand preventing the rechargeable power source from being damaged by heatduring manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-section of a wafer-capped rechargeable powersource according to an embodiment of the present invention.

FIGS. 2A-2F illustrate cross-sections of wafer-capped rechargeable powersources at various stages during the manufacturing process according toan embodiment of the present invention.

FIG. 3 is a flowchart depicting a method of manufacturing a wafer-cappedrechargeable power source according to an embodiment of the presentinvention.

FIG. 4 illustrates a cross-section of a wafer-capped rechargeable powersource according to an embodiment of the present invention.

FIG. 5 illustrates a wafer-capped rechargeable power source integratedin a circuit according to an embodiment of the present invention.

FIG. 6 illustrates a wafer-capped rechargeable power source integratedin a circuit according to an embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention may provide a wafer-cappedrechargeable power source. The wafer-capped rechargeable power sourcemay comprise a device wafer, a rechargeable power source disposed on asurface of the device wafer, and a capping wafer to encapsulate therechargeable power source. The rechargeable power source may include ananode component, a cathode component, and an electrolyte component.

Embodiments of the present invention may provide a circuit with anintegrated rechargeable power source. The circuit may comprise a circuitboard and a device mounted on the circuit board. The device may comprisea device wafer, a rechargeable power source disposed on a surface of thedevice wafer, and a capping wafer attached over the rechargeable powersource forming a cavity between the rechargeable power source and thedevice wafer. The circuit may further comprise a plurality of devicesmounted on the circuit board, wherein the device may be electricallyconnected to at least one of the plurality of devices

Embodiments of the present invention may provide method of manufacturinga wafer-capped rechargeable power source. The method may comprise thesteps of providing a top wafer and a device wafer; forming arechargeable power source on a surface of the device wafer; forming acapping wafer from the top wafer; and attaching the capping wafer overthe rechargeable power source to encapsulate the rechargeable powersource.

FIG. 1 illustrates a cross-section of a wafer-capped rechargeable powersource 100 according to an embodiment of the present invention. Thewafer-capped rechargeable power source 100 may include a device wafer102, a rechargeable power source 103, and a capping wafer 104.

The device wafer 102 may have an active surface and a back surface. Therechargeable power source 103 may be disposed on the back surface of thedevice wafer 102. The rechargeable power source 103 may include acathode current collector 106, a cathode component 108, an electrolytecomponent 114, an anode component 116, and an anode current collector120. In an embodiment, the rechargeable power source 103 may be providedas a battery or a super capacitor (i.e., no dielectric). Other devicesmay be formed on the active side of the device wafer 102.

The electrolyte component 114 may be in the form of an organic materialor an ionic liquid material. When the electrolyte component 114 isformed of an organic material such as propylene carbonate, ethylenecarbonate, or dimethyl carbonate, the cathode current collector 106, thecathode component 108, the anode component 116, and the anode currentcollector 120 may be formed of metals of good conductivity such asaluminum, copper, or gold. When the electrolyte component 114 is formedof an ionic liquid material such as 1-buthyl-3-methylimidazolium([BMIM][Cl]), trioctylmethylam monium bis(trifluoromethylsulfonyl)imide([OMA][TFSI]), or triethylsulfonium bis(trifluoromethylsulfonyl)imide([SET3][TFSI]), the cathode current collector 106, the cathode component108, the anode component 116, and the anode current collector 120 may beformed of porous carbon, graphene, or carbon nanotube.

To prevent the electrolyte component 114 from degrading, exploding, orbeing damaged during the manufacturing process of the wafer-cappedrechargeable power source 100, the capping wafer 104 may be attached tothe device wafer 102 to encapsulate the rechargeable power source 103 ata low temperature, for example below 200° C. As illustrated in FIG. 1,the capping wafer 104 may be attached over the rechargeable power source103 with a bonding material 118, which may be made of bismuth-tinalloys.

Moreover, attaching the capping wafer 104 over the rechargeable powersource 103 in a vacuum chamber or a chamber containing an inert gas suchas nitrogen may form a vacuum or inert gas cavity 122. The vacuum orinert gas cavity 122 further reduces the risk of explosion of therechargeable power source 103. Encapsulating the rechargeable powersource 103 with the capping wafer 104 as described may also create amoisture barrier, which may prevent external moisture from entering thecavity 122, thus preventing corrosion of the different components of therechargeable power source 103. As shown in FIG. 1, the cathode currentcollector 106 and the anode current collector 120 extend outside of thecapping wafer 104 to allow connection to other devices (not shown) forcharging and discharging of the rechargeable power source 103.

A method of manufacturing a plurality of wafer-capped rechargeable powersource, according to an embodiment of the present invention, will now bedescribed with respect to FIGS. 2A-2F, which depict cross-sections ofthe wafer-capped rechargeable power sources at various stages during itsmanufacturing process.

In FIG. 2A, a top wafer 201 and a device wafer 202 may be provided at astage of the manufacturing process. At this stage, the device wafer 202may have already undergone other manufacturing steps such that one orboth surfaces of the device wafer 202 are made to be active. Forexample, the surface(s) or sections of the surface(s) of the devicewafer 202 may have been positively and/or negatively doped. Further atthis stage, a metal layer 205 may be formed on one of the surfaces ofdevice wafer 202. The metal layer 205 may be formed of metals with goodconductivity, such as aluminum, copper, or gold. The thickness of themetal layer 205 may be in the range of a few micrometers (microns).

FIG. 2B depicts a subsequent stage in the manufacturing process, whereportions of the metal layer 205 may be etched to form cathode currentcollectors 206. A cathode layer 207 may be formed over the cathodecurrent collectors 206. The cathode layer 207 may be formed of porouscarbon, graphene, or carbon nanotube. The thickness of the cathode layer207 may be in the range of tens to hundreds of microns. On the otherhand, portions of the top wafer 201 may be etched to form cavities 210and 212 having a depth that is adequate to encapsulate rechargeablepower sources that will eventually be formed.

At the manufacturing stage shown in FIG. 2C, portions of the cathodelayer 207 may be etched to form cathode components 208. An electrolytelayer 213 may be formed over the cathode components 208 and the cathodecurrent collectors 206. The electrolyte layer 213 may be formed of anorganic material such as propylene carbonate, ethylene carbonate, ordimethyl carbonate, or an ionic liquid material such as1-buthyl-3-methylimidazolium ([BMIM][Cl]), trioctylmethylam moniumbis(trifluoromethylsulfonyl)imide ([OMA][TFSI]) or triethylsulfoniumbis(trifluoromethylsulfonyl)imide ([SET3][TFSI]). The thickness of theelectrolyte layer 213 may be in the range of tens to hundreds ofmicrons. With appropriate masking techniques (not shown for brevity),further etching may be carried out to deepen the cavities 212, whilekeeping the depth of the cavities 210 unchanged. This will allow, aswill be shown in a later manufacturing stage, the polishing of the topwafer 201 such that separate capping wafers may be formed.

FIG. 2D depicts a further point in the manufacturing process, where theelectrolyte layer 213 may be etched to form electrolyte components 214,enclosing the cathode components 208. An anode layer 215 may be formedover the electrolyte components 214 and the cathode current collectors206. The anode layer 216 may be formed of porous carbon, graphene, orcarbon nanotube. The thickness of the anode layer 215 may be in therange of tens to hundreds of microns. As shown in FIG. 2D, a bondingmaterial layer 218 may be deposited on the upper horizontal surfaces ofthe top wafer 201. The bonding material layer 218 may be formed ofbismuth-tin alloys. The thickness of the bonding material layer 218 maybe in the range of a few microns.

At the manufacturing stage shown in FIG. 2E, portions of the anode layer215 may be etched to form anode components 216. A metal layer 219 may beformed on the anode components 216, the electrolyte components 214, andthe cathode current collectors 206. The metal layer 219 may be formed ofmetals with good conductivity such as aluminum, copper, or gold. Thethickness of the metal layer 219 may be in the range of a few microns.With appropriate masking techniques (not shown for brevity), the bondingmaterial layer 218 in the cavities 210 and 212 may be removed, whileleaving behind the bonding material layer 218 on remaining surfaces, asshown in FIG. 2E. Additionally, the top wafer 201 may be flippedvertically in preparation to be attached over the rechargeable powersources. A dotted line 221 demarks the level to which the top wafer 201may be polished to form the capping wafers.

FIG. 2F depicts an even further stage in the manufacturing process,where portions of the metal layer 219 may be etched to form anodecurrent collectors 220. At this point in the manufacturing process, therechargeable power sources are formed. Within a vacuum chamber or achamber containing an inert gas, the top wafer 201 may then be attachedover the rechargeable power sources with the bonding material 118 at alow temperature, which may be below 200° C. Cavities 222, which containeither a vacuum or the inert gas, are thus formed. Subsequently, the topwafer 201 may be polished to the dotted line 221 shown in FIG. 2E toform capping wafers 204. The device wafer 202 may then be die cut at adotted line 223 to form the individual wafer-capped rechargeable powersources 200.

It is to be appreciated that, even if FIGS. 2A-2F illustrate themanufacturing of two wafer-capped rechargeable power sources 200, aplurality of wafer-capped rechargeable power sources 200 may be formedsimultaneously on a wafer of any conventional sizes.

FIG. 3 illustrates a method 300 of manufacturing a plurality ofwafer-capped rechargeable power sources according to an embodiment ofthe present invention. The discussion of FIG. 3 will make references toFIGS. 2A-2F, but it should be understood that the method 300 is notlimited to the specific embodiments depicted in FIGS. 2A-2F, but is moregenerally applicable.

As shown in FIG. 3, the method 300 may comprise two paths—one to formrechargeable power sources and the other to form capping wafers—that maymerge to eventually form a plurality of wafer-capped rechargeable powersources (e.g., the wafer-capped rechargeable power sources 200).

The first path of the method 300 begins at step 302 by providing adevice wafer (e.g., the device wafer 202). At step 304, a first metallayer (e.g., the metal layer 205) is formed on one of the surfaces ofthe device wafer. Portions of the first metal layer are etched at step306 to form cathode current collectors (e.g., the cathode currentcollectors 206). At step 308, a cathode layer (e.g., the cathode layer207) is formed over the cathode current collectors. Portions of thecathode layer are etched at step 310 to form cathode components (e.g.,the cathode components 208). At step 312, an electrolyte layer (e.g.,the electrolyte layer 213) is formed over the cathode components and thecathode current collectors. Portions of the electrolyte layer are etchedat step 314 to form electrolyte components (e.g., the electrolytecomponents 214) enclosing the cathode components. At step 316, an anodelayer (e.g., the anode layer 215) is formed over the electrolytecomponents and the cathode current collectors. Portions of the anodelayer are etched at step 318 to form anode components (e.g., the anodecomponents 216). At step 320, a second metal layer (e.g., the metallayer 219) is formed over the anode components, the electrolytecomponents, and the cathode current collectors. Portion of the secondmetal layer are etched at step 322 to form the anode current collectors(e.g., the anode current collectors 220). At this point in themanufacturing process of method 300, the rechargeable power sources areformed.

The second path of the method 300 begins at step 324 by providing a topwafer (e.g., the top wafer 201). At step 326, portions of the top waferare etched to form cavities (e.g., the cavities 210 and 212) that aredeep enough to encapsulate the rechargeable power sources formed at step322. At step 326, with appropriate masking techniques, a selection ofthe cavities formed at step 324 that will not encapsulate anyrechargeable power source (e.g., the cavities 212) are further deepenedby etching. At step 330, a bonding material layer (e.g., the bondingmaterial layer 218) is deposited on the upper horizontal surfaces of thetop wafer, including the horizontal surfaces within the cavities. Withappropriate masking techniques, portions of the bonding material layerin all the cavities are removed (e.g., as shown in FIG. 2E). At thispoint of the manufacturing process of method 300, the top wafer is readyto be attached over the rechargeable power sources formed at step 322.

At step 334, the top wafer in the state described at step 332 isattached over the rechargeable power sources formed at step 322 with thebonding material at a low temperature, which may be below 200° C. Theattachment is carried out within either a vacuum chamber or a chambercontaining an inert gas such that vacuum or inter gas cavities (e.g.,the cavities 222) are formed between the rechargeable power sources andthe top wafer. The top wafer is polished at step 336 to form cappingwafers (e.g., the capping wafers 204). The device wafer is die cut atstep 338 to form a plurality of wafer-capped rechargeable power sources(e.g., the wafer-capped rechargeable power sources 200).

FIG. 4 illustrates a cross-section of a wafer-capped rechargeable powersource 400 according to an embodiment of the present invention. Similarto the wafer-capped rechargeable power source 100 or 200, thewafer-capped rechargeable power source 400 may include a device wafer402, a capping wafer 404, a cathode current collector 406, a cathodecomponent 408, an electrolyte component 414, an anode component 416, abonding material 418, and an anode current collector 420. Thewafer-capped rechargeable power source 400 may be manufactured in asubstantially similar fashion as the wafer-capped rechargeable powersource 100 or 200, using similar materials and under similar conditions.Unlike the wafer-capped rechargeable power source 100 or 200, for agiven power density, the wafer-capped rechargeable power source 400 mayallow for thinner, albeit wider, aspect ratio.

In FIG. 4, the cathode current collector 406 and the anode currentcollector 420 may be formed on the device wafer 402. The cathodecomponent 408 and the anode component 416 may then be formed on thecathode current collector 406 and the anode current collector 420,respectively. As can be seen in FIG. 4, the cathode component 408 andthe anode component 416 may substantially be formed in a same horizontalplane. The electrolyte component 414 is formed over the cathodecomponent 408 and the anode component 416, effectively forming arechargeable power source. The capping wafer 404 may be attached overthe rechargeable power source with the bonding material 418 at a lowtemperature, which may be below 200° C.

FIG. 5 illustrates a wafer-capped rechargeable power source 500integrated in a circuit according to an embodiment of the presentinvention. Similar to the wafer-capped rechargeable power source 100 or200, the wafer-capped rechargeable power source 500 may include a devicewafer 502, a capping wafer 504, a cathode current collector 506, acathode component 508, an electrolyte component 514, an anode component516, a bonding material 518, and an anode current collector 520.Additionally, the wafer-capped rechargeable power source 500 includesthrough-hole vias 526 such that the wafer-capped rechargeable powersource 500 may be electrically connected to traces 530 and 532 of acircuit board 524 via solder balls 528.

The trace 530 may effectively connect to the cathode current collector506 and the trace 532 to the anode current collector 520. The traces 530and 532 may be routed and connected to at least one of a plurality ofdevices formed or mounted on the circuit board 524. For example, in FIG.5, the traces 530 and 532 may be connected to devices 534 and 536. Thedevices 534 and 536 may either be powered by the wafer-cappedrechargeable power source 500 or provide power to charge thewafer-capped rechargeable power source 500. For example, the device 534may be a photodiode harvesting electromagnetic energy, which may then bestored in the wafer-capped rechargeable power source 500, and the device536 may be a light-emitting diode (LED) with appropriate powerconditioning components to convert power from the wafer-cappedrechargeable power source 500 to light up the LED.

The circuit in FIG. 5, including the wafer-capped rechargeable powersource 500, may be subsequently potted or enclosed in a plastic molding.Despite the typical high temperatures needed for plastic molding orpotting, the capping wafer 504 may shield the rechargeable power sourceand prevents it from being degraded.

FIG. 6 illustrates a wafer-capped rechargeable power source 600integrated in a circuit according to an embodiment of the presentinvention. Similar to the wafer-capped rechargeable power source 100 or200, the wafer-capped rechargeable power source 600 may include a devicewafer 602, a capping wafer 604, a cathode current collector 606, acathode component 608, an electrolyte component 614, an anode 616, abonding material 618, and an anode current collector 620. Additionally,the wafer-capped rechargeable power source 600 includes through-holevias 626 such that the wafer-capped rechargeable power source 600 may beelectrically connected to traces 630 and 632 on an opposite activesurface of the device wafer 602. The trace 630 may effectively connectto the cathode current collector 606 and the trace 632 to the anodecurrent collector 620.

In FIG. 6, the traces 630 and 632 are shown to be connected to a singledevice 638 formed on the active surface of the device substrate 602.However, one skilled in the art would appreciate that the traces 630 and632 may be connected to a plurality of devices that may be formed on theactive surface of the device substrate 602. As in the circuit shown inFIG. 5, the wafer-capped rechargeable power source 600 may eitherprovide power to or be charged by devices on the active surface of thedevice substrate 602.

Similar to the circuit in FIG. 5, the circuit in FIG. 6, including thewafer-capped rechargeable power source 600, may be subsequently pottedor enclosed in a plastic molding. Despite the typical high temperaturesneeded for plastic molding or potting, the capping wafer 604 may shieldthe rechargeable power source and prevents it from being degraded.

Below is an explanation of certain terms used in this disclosure:

The term “etch” or “etching” is used herein to generally describe afabrication process of patterning a material, such that at least aportion of the material remains after the etch is completed. Forexample, it should be understood that the process of etching siliconinvolves the steps of patterning a masking layer (e.g., photoresist or ahard mask) above the silicon, and then removing the areas of silicon nolonger protected by the masking layer. As such, the areas of siliconprotected by the mask would remain behind after the etch process iscomplete. However, in another example, etching may also refer to aprocess that does not use a mask, but still leaves behind at least aportion of the material after the etch process is complete.

The terms “forming,” “form,” “deposit,” or “dispose” are used herein todescribe the act of applying a layer of material to the substrate oranother layer of material. Such terms are meant to describe any possiblelayer-forming technique including, but not limited to, thermal growth,sputtering, evaporation, chemical vapor deposition, epitaxial growth,electroplating, etc. According to various embodiments, for instance,deposition may be performed according to any appropriate well-knownmethod. For instance, deposition can comprise any process that grows,coats, or transfers material onto a substrate. Some well-knowntechnologies include physical vapor deposition (PVD), chemical vapordeposition (CVD), electrochemical deposition (ECD), molecular beamepitaxy (MBE), atomic layer deposition (ALD), and plasma-enhanced CVD(PECVD), amongst others.

The “substrate” or “wafer” as used throughout the descriptions is mostcommonly thought to be silicon. However, the substrate or wafer may alsobe any of a wide array of semiconductor materials such as germanium,gallium arsenide, indium phosphide, etc. In other embodiments, thesubstrate or wafer may be electrically non-conductive such as glass orsapphire.

As used herein, “mask” or “masking” may comprise any appropriatematerial that allows for selective removal (e.g., etching) of anunmasked portion a material. According to some embodiments, maskingstructures may comprise a photoresist such as Poly(methyl methacrylate)(PMMA), Poly(methyl glutarimide) (PMGI), a Phenol formaldehyde resin, asuitable epoxy, etc.

Several embodiments of the invention are specifically illustrated and/ordescribed herein. However, it will be appreciated that modifications andvariations of the invention are covered by the above teachings andwithin the purview of the appended claims without departing from thespirit and intended scope of the invention.

What is claimed is:
 1. A device, comprising: a device wafer; arechargeable power source disposed on a surface of the device wafer, therechargeable power source including an anode component, a cathodecomponent, a current collector, and an electrolyte component; and acapping wafer coupled to the device wafer and configured to encapsulatethe rechargeable power source in a cavity, wherein the current collectorextends from inside the cavity to outside the cavity.
 2. The device ofclaim 1, further comprising an inert gas provided in the cavity.
 3. Thedevice of claim 1, further comprising a vacuum provided in the cavity.4. The device of claim 1, further comprising a bonding material bondingthe capping wafer to the device wafer.
 5. The device of claim 1, whereinthe electrolyte component includes an organic material.
 6. The device ofclaim 1, wherein the electrolyte component includes an ionic liquidmaterial.
 7. The device of claim 1, wherein the current collector is afirst current collector and the cathode component is formed on the firstcurrent collector on the device wafer, wherein the anode component isformed on a second current collector on the device wafer, and theelectrolyte component is formed on the cathode component and the anodecomponent, the second current collector extending from inside the cavityto outside the cavity.
 8. The device of claim 7, wherein the cathodecomponent and anode component are substantially formed in a samehorizontal plane.
 9. A circuit, comprising: a circuit board; and adevice mounted on the circuit board, the device comprising: a devicewafer, a rechargeable power source disposed on a surface of the devicewafer and including a current collector, and a capping wafer attachedover the rechargeable power source forming a cavity between therechargeable power source and the capping wafer, wherein the currentcollector extends from inside the cavity to outside the cavity.
 10. Thecircuit of claim 9, wherein the device is directly mounted on thecircuit board with solder balls.
 11. The circuit of claim 9, wherein thedevice is directly mounted on the circuit board with through-hole vias.12. The circuit of claim 9, wherein the circuit further comprises aplurality of devices mounted on the circuit board, and wherein thedevice is electrically connected to at least one of the plurality ofdevices.
 13. The circuit of claim 9, wherein the cavity is filled withan inert gas.
 14. A device, comprising: a device substrate; arechargeable power source disposed on a surface of the device substrate,the rechargeable power source including an anode, a cathode, a currentcollector, and an electrolyte; and a capping wafer coupled to the devicesubstrate and defining, at least in part, a cavity in which therechargeable power source is disposed, wherein the current collectorextends from inside the cavity to outside the cavity.
 15. The device ofclaim 14, further comprising an inert gas in the cavity.
 16. The deviceof claim 14, further comprising a vacuum in the cavity.
 17. The deviceof claim 14, wherein the capping wafer is attached over the rechargeablepower source with a bonding material.
 18. The device of claim 14,wherein the electrolyte includes an organic or ionic liquid material.19. The device of claim 14, wherein the current collector is a firstcurrent collector and the cathode is formed on the first currentcollector on the device substrate, wherein the anode is formed on asecond current collector on the device substrate, and the electrolyte isformed on the cathode and the anode.
 20. The device of claim 14, whereinthe cathode and anode are substantially formed in the same horizontalplane.
 21. A capped rechargeable power source disposed on a surface of adevice substrate, the capped rechargeable power source comprising: acapping wafer forming, at least in part, a cavity; and a rechargeablepower source disposed in the cavity, comprising: an anode; a cathode; anelectrolyte electrically coupled between the anode and cathode; and acurrent collector coupled to the anode or cathode and extending frominside the cavity to outside the cavity.
 22. The capped rechargeablepower source of claim 21, further comprising an inert gas or vacuum inthe cavity.
 23. The capped rechargeable power source of claim 21,wherein the capping wafer is coupled to the device substrate with abonding material.
 24. The capped rechargeable power source of claim 21,wherein the electrolyte includes an organic or ionic liquid material.25. The capped rechargeable power source of claim 21, wherein thecurrent collector is a first current collector and the cathode is formedon the first current collector on the device substrate, wherein theanode is formed on a second current collector on the device substrate,and the electrolyte is formed on the cathode and the anode.
 26. Acircuit, including a capped rechargeable power source disposed within acavity and on a surface of a device substrate, and including a currentcollector, the circuit comprising: a capping wafer forming, at least inpart, the cavity; a circuit board; and the capped rechargeable powersource coupled to the circuit board; wherein the current collectorextends from inside the cavity to outside the cavity.
 27. The circuit ofclaim 26, wherein a device comprising the capped rechargeable powersource is directly mounted on the circuit board with solder balls. 28.The circuit of claim 26, wherein a device comprising the cappedrechargeable power source is directly mounted on the circuit board withthrough-hole vias.
 29. The circuit of claim 26, wherein the circuitfurther comprises a plurality of devices mounted on the circuit board,and wherein the capped rechargeable power source is electricallyconnected to at least one of the plurality of devices.
 30. The circuitof claim 26, wherein the cavity is filled with an inert gas or vacuum.